When ensuring the protection of the power grid from all kinds of failures, various devices and mechanisms are used. Among them are automated switches that prevent serious electrical failures and keep household appliances from being damaged. To understand the principle of operation of a circuit breaker, you need to understand its design and technical characteristics.
Content
- Basic types
- Principle of operation and device
- Design features
- Modes of operation
- Short circuit response
- Useful Tips
Basic types
Externally, the element is a small structure made of heat-resistant plastic, on the front of which there is a special switch, and in the back there is a latch-lock. There are screw terminals at the top and bottom. Depending on design features and device, circuit breakers can be divided into the following types:
- Installation models - equipped with a plastic box, which allows them to be used for all dwellings without fear of electric shock.
- Universal aggregates - do not have the same protection as the previous version, which is why they are used only in special conditions, equipping distribution equipment.
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High-speed switches - are characterized by an incredible speed of response to problems in the electrical circuit. According to manufacturers, the speed is 5 milliseconds. - Delayed devices - the response speed varies between 10-100 milliseconds.
- Selective - are characterized by support for adjusting the shutdown mode.
- Reverse current electric models - capable of operating only when the direction of the current changes in a certain range.
- Polarized parts - turn off that section of the circuit in which a significant jump in the current intensity is noticed.
- Unpolarized - they work like the previous varieties, but are not limited to one direction of current.
As for the shutdown speed, it is determined by the principle of operation of the machine, as well as the corresponding conditions for de-energizing a specific section. They are created by electrical equipment and current-limiting elements.
Principle of operation and device
The principle of operation, design and other features of the circuit breaker are determined by the scope of operation and the tasks for which it is intended. The equipment is switched on and off both manually and using a special drive.
The first starting option is available in protective models that operate with amperage up to 1 thousand. ampere. They are characterized by a high switching capacity, which does not depend in any way on the intensity of the handle movement. In the event of an emergency, the circuit breaker independently disconnects the circuit, which leads to the start of the free-release mechanism.
An irreplaceable element of the unit is the release. Its task is to control the operating properties of a certain section of the circuit and influence the switch under unforeseen circumstances. In addition, the release is capable of remotely disconnecting the machine, which is important when servicing complex and powerful circuits. There are such types of similar elements:
- Electromagnetic - capable of protecting the wiring circuit from short circuits.
- Thermal - prevent the effects of intense surges in current strength.
- Mixed.
Semiconductor switches are also commercially available, which are characterized by easy adjustment and stable settings. They are used in the electrical circuits of apartment buildings and cottages.
If it becomes necessary to connect the circuit without being connected to the mains, you can dispense with circuit breakers without trip units. Today, hundreds of models and types of switches are available on the market, which are suitable for various operating environments and are not afraid of super-intensive use. Individual series withstand maximum loads and are not afraid of environmental influences.
When choosing a suitable circuit breaker, you must first familiarize yourself with the documentation that comes with it. This will allow you to find the best option for your home network.
Design features
Dealing with the principle of the "machine", it is important to know about the main components of which it consists. Most models work based on such nodes:
- Release system.
- Contact connections.
- Control node.
- Arc extinguishing device.
- Releases.
The contact system is a connection of static and dynamic contacts, which are closed in a special casing. The dynamic contacts are held by hinges on the shaft of the handle. Their task is to implement a single disconnection of a section of the circuit.
The arc extinguishing device is located in two poles and is designed to capture the arc and cool it. By its design, the mechanism is an arc extinguishing chamber with a deionic lattice of plates. As far as the decoupling system is concerned, it is a hinge component with three or four links. With its help, instantaneous release and shutdown of the contact system is carried out. Fields of application include both manual devices and automatic ones.
The task of the electromagnetic release is to turn off the entire system in the event of a short circuit. By design, it is an ordinary electromagnet with a special hook. Some models may have a hydraulic braking system. There is another type of release - thermal. The element is a small metal plate that deforms when exposed to an increased voltage level and initiates the shutdown process.
The semiconductor elements are the measuring sensor, magnet and relay box. The magnet acts on the entire system, and the measuring sensor consists of an AC transformer or a DC amplifier.
Most of the models of protective devices are equipped with trip units that operate on the basis of thermocouples to protect against overcurrent, as well as magnetic coils to prevent short closures.
Protective structures have several components located inside or outside the machine. These include all kinds of releases and contacts, drives for remote control, signaling equipment and automatic shutdown sensors.
Modes of operation
During normal operation, the circuit breaker passes current at a current strength that corresponds to the normal level. The electricity used to operate the device is supplied to the top terminal. In turn, this terminal interacts with a static contact, which transfers current to the dynamic contact, the metal conductor and directly to the solenoid coil.
Once in this coil, electricity begins to flow through the thermal release and then penetrate the terminal at the bottom of the protective equipment. In the event of a significant voltage surge or increased risk of short circuit, the circuit breaker automatically stops the operation of the network.
If an overload occurs in the circuit, the element works according to a different principle. This phenomenon is noticed with a strong increase in the current strength in a specific area, which exceeds the permissible value several times. Upon contact with a thermal release, this current begins to deform it, which becomes a signal to turn off the machine.
This type of protection is not able to work instantly, since the process of deformation of the plate takes some time and requires sufficient heating. The shutdown speed is determined by the excess current in the protected area and takes a time interval from a few seconds to an hour. Due to such a delay, unnecessary shutdowns of the machine due to minimal and short surges are practically excluded. In most cases, these surges occur when starting electrical appliances with high inrush currents.
As for the indicators at which the thermal element begins to work, they are regulated by a special part and are adjusted even during the production of the element. The best option is a value that is 1.1-1.5 times the normal number.
You also need to take into account the fact that in buildings with elevated temperatures, the circuit breaker can malfunction, since in such conditions the metal plate lends itself to deformation much faster. In a cold environment, everything happens in the opposite order - the switch does not respond to voltage surges for too long.
Short circuit response
Modern switches are able to secure the network not only against voltage surges and overloads, but also against frequent short circuits. As you know, such incidents increase the intensity of the current to the temperature at which the process of melting the insulation of the wiring begins. But such an incident entails dangerous consequences and can lead to a fire situation. To avoid the formation of short circuits, you need to turn off the electricity in time. It is for these purposes that the switch is used.
The device consists of a solenoid coil and a core, which is fixed by means of a small spring. When an unexpected power surge occurs, the magnetic induction begins to rise. In this regard, the contacts are instantly opened, and the supply of electric current to the protected area is suspended. The electromagnetic component turns on in a few milliseconds and prevents the insulation from igniting.
When the contacts are disconnected, an arc is formed between them with a temperature of up to 3 thousand. degrees. Naturally, household appliances are not able to withstand the effects of such a temperature regime, therefore, protective machines are additionally equipped with an arc extinguishing element, which resembles a box made of metal records.
Useful Tips
If the start of the electrical equipment was caused by a short circuit, then it will not be possible to restore the electricity without eliminating the cause of the breakdown. Often, a problem occurs when some household appliance is damaged, therefore, in order to return everything to their places, it is enough to disconnect the failed device from the network, and then restart switch. Upon successful completion of such a task, the system should work again. And if this did not happen, then you will have to seek help from specialists and determine the original source of the breakdown.
Faced with the problem of frequent shutdowns of protective elements, there is no need to rush to buy a new device with higher amperage rates - the problem will not disappear from this. Indeed, at the stage of installing the switches, the cross-sectional area of the wire is taken into account, therefore, an excessively high current will not appear in the wiring.
To determine the cause of the breakdown and further action, you should call a specialist, but do not try to do everything yourself. In most cases, independent actions do not give any good results, and sometimes lead to disastrous consequences.
Unfortunately, fire situations occur too often, and often they are caused by the negligence of consumers who do not follow the basic rules for handling electrical appliances and electricity in general. But it is much wiser to prevent the consequences of a fire than to bitterly regret what happened later.
And if in the recent past protection against short circuits and overload was carried out by classic fuses from porcelain with replaceable inserts, as well as corks, today this is solved with the help of an automated equipment. When choosing such an element, you need to familiarize yourself in advance with its technical characteristics and compatibility with a particular circuit. A high-quality automatic protection device will be able to save household appliances from damage, and a home from a fire hazard.
